CALORIMETRIC STUDY OF FLUORINATED METHACRYLIC AND VINYL POLYMER BLENDS .1. BINARY-SYSTEMS - DETERMINATION OF MISCIBILITY DOMAINS AND CORRELATION OF GLASS-TRANSITION TEMPERATURES WITH BLENDS COMPOSITION - APPLICATION TO PLASTIC OPTICAL-FIBER CLADDING

This paper reports a calorimetric study of binary polymer blends prepa red by solution mixing of fluoroalkyl methacrylic ester-methyl methacr ylate (MMA) copolymers with poly(vinylidene difluoride) (PVDF) or VDF- hexafluoropropene (HFP) (or VDF-trifluoroethylene) copolymers and exam ines their use as materials in plastic optical fibres (POF) technology . Some interesting blends were also obtained through mechanical mixing in the molten state. As compared to the well known PVDF-poly(methyl m ethacrylate) (PMMA) system, miscibility domains in copolymer blends be come wider when less crystalline VDF copolymers are used in place of P VDF, whereas the opposite is found for the introduction of fluorinated alkyl ester side chains in PMMA. Correlation of the observed glass tr ansition temperatures of homogeneous phases to their compositions fail ed with the Fox and Gordon-Taylor relations, whereas good fits could b e observed using both Kwei and Jenckel-Heutsch relations. The q and b (specific interactions) parameters in these relations are well correla ted to the chemical composition, indicating the influence of strong in termolecular interactions. In fluoroalkyl methacrylic ester-containing polymers, internal interactions are competing efficiently with interm olecular ones, thus limiting the miscibility of these polymers with VD F-homo- and copolymers. Some blends of the MMA-trifluoromethyl methacr ylate with VDF-HFP copolymers give good performances as POF cladding m aterial. A more simple solution lies in the use of VDF-HFP copolymers themselves. (C) 1997 Elsevier Science Ltd.